Caldiz, Furnace of Zendikar

Caldiz, Furnace of Zendikar enters the battlefield
tapped with 30 stone counters on it. As long as
it has a stone counter on it it is a land.
At the beginning of each player's end step,
remove X stone counters from Caldiz, Furnace
of Zendikar. If there are no stone counters on
it, add X +1/+1 counters to it instead. X is equal
to the number of tapped permanents that player
controls.